1. Field of the Invention
The present invention relates to a cup attaching apparatus for attaching a cup used for machining a peripheral edge of an eyeglass lens, to the lens to be machined (processed).
2. Description of Related Art
For machining a peripheral edge of an eyeglass lens, a cup attaching apparatus is used to attach a cup to the surface of a lens to be machined (a workpiece lens). This cup serves as a machining jig for holding the workpiece lens on a lens chuck shaft of a lens edge machining device. The cup attaching apparatus is also called a blocker. As this type of cup attaching apparatus, there is known an apparatus provided with a screen on which an image of the workpiece lens is projected by illumination light emitted from an illumination light source. By observing the lens image (an image of a mark applied on the lens, an image of a double focus lens, etc.) projected on the screen and an alignment mark formed on the screen, an operator adjusts the position of the lens to a desired relationship with a reference axis for cup attachment and then presses an arm in which the cup is previously set, thereby attaching the cup to the surface of the lens (e.g., see U.S. Pat. No. 7,150,672 (JP2002-283202A)).
In the above type of apparatus, heretofore, a halogen lamp or a xenon lamp has been used as an illumination light source. However, those lamps have a short life, requiring frequent replacement of lamps. In recent years, a high-luminance white LED has been in practical use and available at low cost. It is accordingly conceivable to use such a white LED having a long life as the illumination light source.
However, when the white LED was used as the illumination light source of the cup attaching apparatus, the following disadvantages were found. The white LED has emission characteristics that the intensity of a blue wavelength component is higher and the intensity of a red wavelength component is relatively slightly low than those of a halogen lamp. Accordingly, a colored lens such as sunglass lens having particularly a red wavelength component with a low transmittance causes a large decrease in amount of illumination light allowed to pass through the lens, resulting in a dark image projected on the screen and thus deteriorating visibility of the mark image on the lens. In the case of a transparent lens having a high transmittance, to the contrary, when the light intensity of the white LED is set to be higher to enhance the visibility with the colored lens, the illumination light of the high-luminance white LED is so strong that the image projected on the screen causes glare to an operator, leading to a burden on the eyes of the operator. Further, the white LED has a property of immediately increasing the light intensity up to a set value as soon as the LED is turned on. Particularly, in the case where the cup attaching apparatus is used in a dark place and also due to the high intensity of the blue wavelength component, the illumination light at turn-on tends to stimulate the eyes, which would be a large burden to the eyes.